(1) Field of the Invention
The present invention relates to cultured cells and a tissue-culturing method, and particularly the invention relates to cultured cells of Rhaphiolepis umbellata Thunb. and a method for culturing tissues of the Rhaphiolepis umbellata Thunb. by using said cultured cells.
(2) Related Art Statement
Recently, investigations have been vigorously carried out on the tissue culturing of the higher plants, and techniques for mass culturing plant tissues removed from leaves, stems, roots, etc. have public attracted attentions. When a plant piece cut off is place on agar or in a liquid containing a nutriment, a mass of cells swell up from a cut edge of the plant piece. This is called callus.
In general, cells of different tissues, for example, tissues of a root and a leaf, have different shapes and functions, respectively. This results from gradual differentiation during a time period in which the cells grow. However, the callus continue to grow without differentiation.
Generally, seeding or cutting-planting must be done so as to propagate plants. Further, the soil and the environment largely influence the growth of the plants. However, the culturing of the callus is not influenced by changes in these matters. In addition, the callus grows faster than ordinary plant bodies. When a hormone or a chemical substance that promotes germination or rooting is added to the callus, a complete plant body is obtained.
As such a callus tissue-culturing method, methods for culturing tissues of trees such as poplar and eucalyptus are known.
However, what has been established as the tissue-culturing methods are limited to the kinds of trees such as poplar and eucalyptus only. One of reasons for this is that it is difficult to grow or root other breeds unless appropriate hormones or the like are used.
The Rhaphiolepis umbellata Thunb., which is a plant belonging to the Rosaceae, is a roadside tree planted in a median strip of a road, etc. The Rhaphiolepis umbellata Thunb. is strong against the public pollution, and has saline resistance. In order to assuredly and swiftly provide such plants having strong public pollution resistance, the tissue-culturing method is effective. However, a method for stably mass propagating the Rhaphiolepis umbellata Thunb. has not been established.
It is an object of the present invention to provide cultured cells and a tissue-culturing method, which enable the establishment of stable mass propagation and transformation system of the Rhaphiolepis umbellata Thunb.
In order to accomplish the above object, the present inventors had repeatedly made strenuous investigations on conditions suitable for inducing the formation of callus and the redifferentiation of the Rhaphiolepis umbellata Thunb., and consequently have come to discover the cultured cells and the tissue-culturing method according to the present invention.
The cultured cell according to the present invention has high differentiating power, and is obtained by culturing a part of a tissue of the Rhaphiolepis umbellata Thunb. in a culture medium containing benzyladenine and naphthaleneacetic acid (NAA) in an amount effective to induce callus formation of the Rhaphiolepis umbellata Thunb.
In a preferred embodiment of the cultured cell of the Rhaphiolepis umbellata Thunb. according to the present invention, the tissue of the Rhaphiolepis umbellata Thunb. is a tissue selected from the group consisting of a shoot apex, a stem, a leaf, an embryonic cell and a root.
In another preferred embodiment of the cultured cell of the Rhaphiolepis umbellata Thunb. according to the present invention, the tissue of the Rhaphiolepis umbellata Thunb. is a tissue originated from a plant body raised from a seedling obtained by germinating a sterilized seed of the Rhaphiolepis umbellata Thunb.
In a further preferred embodiment of the cultured cell of the Rhaphiolepis umbellata Thunb. according to the present invention, the tissue of the Rhaphiolepis umbellata Thunb. is a tissue less than 2 weeks after seeding the Rhaphiolepis umbellata Thunb.
In a still further preferred embodiment of the cultured cell of the Rhaphiolepis umbellata Thunb. according to the present invention, the tissue of the Rhaphiolepis umbellata Thunb. is a tissue obtained by aseptically growing a seed of the Rhaphiolepis umbellata Thunb.
In a still further preferred embodiment of the cultured cell of the Rhaphiolepis umbellata Thunb. according to the present invention, the culture medium is a WP culture medium or an MS culture medium.
The method for culturing a tissue of a Rhaphiolepis umbellata Thunb. according to the present invention comprises the steps of subculturing any of the above cultured cells in a culture medium containing benzyladenine and naphthaleneacetic acid (NAA) in an amount effective to induce callus formation of the Rhaphiolepis umbellata Thunb., and thereby obtaining plantlet of the Rhaphiolepis umbellata Thunb.
In a preferred embodiment of the Rhaphiolepis umbellata Thunb. tissue-culturing method according to the present invention, the culture medium is a WP culture medium or an MS culture medium.
The cultured cell according to the present invention is a cultured cell of the Rhaphiolepis umbellata Thunb. having high differentiating power, said cultured cell being obtained by culturing a part of a tissue of the Rhaphiolepis umbellata Thunb. in a culture medium containing benzyladenine and naphthaleneacetic acid (NAA) in an amount effective to induce callus formation of the Rhaphiolepis umbellata Thunb. In general, the plantlet is formed according to the tissue-culturing method in the course of (1) formation of the callus, (2) formation of a polyblast, (3) redifferentiation of the polyblast and (4) formation of the plantlet. The tissue culturing of the Rhaphiolepis umbellata Thunb. takes this formation course. Here, the term xe2x80x9cpolyblastxe2x80x9d means a mass of numerous shoots in which cells are differentiated.
In the following, the cultured cells of Rhaphiolepis umbellata Thunb. and the tissue-culturing method therefor according to the present invention will be explained.
Although the tissues of the Rhaphiolepis umbellata Thunb. are not particularly limited, tissues from stems, leaves, roots, stem apexes, root apexes, embryonic cells, etc. may be recited. Stems, leaves, roots, stem apexes, embryonic cells and roots are preferred.
The tissues of the Rhaphiolepis umbellata Thunb. may be ones taken from a matured tree of the Rhaphiolepis umbellata Thunb. Preferably, the tissue is a tissue originated from a relatively young cell tissue obtained after seeding the Rhaphiolepis umbellata Thunb. For example, the tissue obtained 2 weeks, more preferably less than 9 to 10 days, after seeding the Rhaphiolepis umbellata Thunb.
Seeds of the Rhaphiolepis umbellata Thunb. can be aseptically germinated and grown on the culture medium. The aseptic treatment for the cutting is not particularly limited, for example, such a treatment can be effected by treating the tissue with ethanol or the like for a few or several hours and with sodium hypochlorite for a few or several hours and is washed with sterilized water. It is preferable to use a seed fed with water at 4 to 10xc2x0 C. in dark for not less than 1 to 3 nights.
The cultured cells of the present invention can be obtained by culturing a part of the tissue as mentioned above, in a culture medium containing benzyladenine and naphthaleneacetic acid (NAA) in an amount effective to induce callus formation of the Rhaphiolepis umbellata Thunb. The amount of benzyladenine depends upon the culture medium used and the culturing condition, and is preferably 0.5 to 10.0 xcexcM, more preferably 0.5 to 5.0 xcexcM. The reason for this range is to enhance the redifferentiation percentage. The amount of naphthaleneacetic acid (NAA) is not particularly limited, but is preferably 0.1 to 1 xcexcM. The reason for this range is also to enhance the redifferentiation percentage.
As the culture medium, culture media such as a WP culture medium, an MS culture medium, a white culture medium and a modified culture medium may be recited. The WP culture medium is a cultured medium obtained by improving the MS culture medium for the purpose of the stem-tip culturing and mass culturing of ericaceous Kalmia latiflora. The MS culture medium is a culture medium developed aiming at the propagation of the marrow tissues and the callus of tobacco. In culturing the Rhaphiolepis umbellata Thunb., the WP culture medium is preferred from the standpoint of enhancing the callus formation rate and the redifferentiation percentage.
In addition, the culture medium may contain trace amounts of organic substances, carbonaceous sources, etc. usually used in culturing. As the organic substances used in a trace amount, vitamins B1, B6, other vitamins such as nicotine acid, thiamine hydrochloride, and pyridoxine hydrochloride, etc.; amino acids such as glycin, asparagine, etc.; hexavalent alcohols such as inosital, sorbit, etc. may be used.
As the carbonaceuous source, saccharides such as sucrose, glycose, etc.; may be recited.
The tissue piece planted in the culture medium can be cultured in a bright condition or a dark condition in a temperature range of 22 to 28xc2x0 C. The temperature condition is preferably 24 to 26xc2x0 C. Callus begins to be formed about one week after the culturing, and the callus is completely formed about 3 to 4 weeks after the culturing. The stable callus is obtained by subculturing at a subculturing interval of about 10 to 20 days.
According to the tissue-culturing method of the present invention, a plantlet of the Rhaphiolepis umbellata Thunb. can be obtained by subculturing the cultured cell having high differentiating power in a culture medium containing benzyladenine and naphthaleneacetic acid (NAA) in an amount effective to induce callus formation of the Rhaphiolepis umbellata Thunb. As to the amounts of benzyladenine (TDZ) and naphthaleneacetic acid (NAA), the above-mentioned condition employed in culturing the cultured cells can be used.
As the cultured cells of the Rhaphiolepis umbellata Thunb. having high differentiating power, the above-mentioned cultured cells according to the present invention can be used.
The growth of the plantlet can be promoted by cutting out a polyblast and coating its cut edge with indoleacetic acid, for example.
As a support for the culture medium, pearlite, vermiculite, Gellan Gum, agar, agarose, etc. may be recited.